The present invention relates to a method for optically detecting the measurements, in particular the diameters, of a long object during the production or following the production, which object moves continuously and at high speed in lengthwise direction. In addition, the invention relates to an arrangement for realizing this method.
For the production of long objects, for example pipes, cables or the like, the accuracy to size and in particular the diameter of such products represents a critical quality control factor. As is known, the accuracy to size of these products must be monitored during the production by using corresponding measuring methods, so-to-speak in real time, and the production parameters adapted, if necessary, to avoid a high number of rejections and thus achieve a high economy for the production method.
Given the present state of the technology, non-contacting optical measuring methods are also used for this xe2x80x9creal timexe2x80x9d control. In order to monitor the diameters during the production of long products, these measuring methods preferably use the principle of xe2x80x9cshadow measuring.xe2x80x9d With this principle, the shadow of a light beam intersecting with the object is detected as measuring value for the diameter.
With rotation-symmetrical or oval products, optical measuring methods using at least two light beams have prevailed. For these methods, a first light beam intersects with the object to be measured at a specific angle while a second light beam also strikes the object at a specific angle. Both light beams in turn are offset relative to each other by a specific angle. The shadows detected in the process as measured values are correlated in real time and compared to actual parameters.
With the methods known from prior art, the light beams preferably strike the product moving along at relatively high speed with relatively steep angles of inclination. This is not a problem with products such as insulated electric cables, extruded pipes or the like, which have a smooth or uniform peripheral surface because technologically the outer diameter is always measured via the shadow formation.
Measuring methods of this type, however, lead to faulty results for products that distinguish themselves through specific peripheral surface structures since the shadow formation does not necessarily correspond to the basic object diameter. Methods of this type therefore present problems, for example when producing concrete reinforcing steel rods. Concrete reinforcing steel rods have ridges or similar profiles on their peripheral surfaces, which do not extend over the complete peripheral surface, but in most cases are offset relative to each other on opposite sides of the rod and are arranged at specific angles of inclination.
If light beams used for the optical measuring strike concrete reinforcing steel rods of this type at relatively steep angles, different shadow values are obtained, depending on whether a ridge or a surface contour is hit.
The production of such long rods or other long products made of steel furthermore carries a certain potential for danger, which so far has prevented the use of such optical detection methods for detecting the diameter of these products during production.
The products, in particular concrete reinforcing steel rods, are rolled while red-hot in the steel rolling plant and at high speeds that can be in the range of 100-200 km/h. Owing to the high rolling speeds, it is absolutely necessary that guides be used for these objects while they are exposed.
To use the optical measuring methods known from prior art, however, the red-hot product must travel at least over a specific distance while exposed, so as to be accessible to the optical measuring device and its light beams for the purpose of obtaining a perfect measurement.
Owing to the fact that the moving red-hot object is easily deformed, the danger exists that when leaving the steel rolling plant the object is deformed in the exposed path section and therefore does not correctly meet a guiding device, located opposite the steel-rolling plant. Instead, it collides with this guide, so that several hundred meters of red-hot material can pile up within a few seconds, thereby resulting in danger to people and measuring devices in the immediately surrounding area.
Starting with these disadvantages, it is the object of the present invention to provide a method as well as an arrangement for realizing this method, which permit an optical detection of the measurements of long products moving at a very high speed, in particular red-hot concrete reinforcing steel rods with surface profiles, without having to reduce the present production speeds.
According to the invention, this object is solved with a method for optically detecting during the production or following the production the measurements of a long object moving continuously at high speed in lengthwise direction. The method comprises providing one light beam to intersect with the object at a first angle at a measuring location and for a second light beam to intersect with the object at a second angle at the same measuring location and detecting the shadows formed in the process. The light beams are offset relative to each other in a cross-sectional plane that is perpendicular to the longitudinal axis of the object by a third angle. The first and second angles are flat angles and the first angle corresponds at least approximately to the second angle.
Surface profiles such as ridges on the concrete reinforcing steel rods can mostly be ignored because the invention provides that the light beams no longer strike the object with a steep angle at the measuring location, but intersect with the object at a flat angle, preferably 10 to 40xc2x0 C. and in particular essentially 20xc2x0. Thus, when using a method of this type, the diameter values are no longer distorted by the ridge structure. Of course, the angles of incidence for the light beams can vary, depending on the different surface designs or profiles, so that their effect on the shadow formation can be compensated accordingly.
For one preferred embodiment, these light beams rotate around the longitudinal axis of the moving object, such that they perform a gyroscope movement, wherein a fixed point or reference point for this gyroscope movement is at the measuring location.
The gyroscope movement of another preferred embodiment is limited, such that the light beams oscillate back and forth by a specific angle.
In both embodiments, the complete peripheral surface or oval shape of the object is measured in this way, wherein the corresponding measured values for the shadows of both light beams are always correlated to each other.
Laterally deflected light beams, preferably laser beams, are used for this.
The invention provides for an arrangement to realize this method, in which the moving red-hot object is guided inside a protective device, arranged between the light sources on the one side and the corresponding receivers on the opposite side of the complete optical measuring device. The measuring location is located inside the protective device. For this, the protective device is provided with a first and a second slot that extend completely through the protective device.
The slots extend through the protective device at angles that match the angles of incidence for the light beams, so that these can pass through the slots without being refracted and can intersect the object inside the protective device at the measuring location. In the same way as the light beams, the slots in the protective device are aligned relative to each other by a corresponding angle in the projection plane that is perpendicular to the longitudinal axis of the moving object.
The protective device for one preferred embodiment is positioned inside a holder, such that it can rotate around the longitudinal axis of the object passing through. Thus, it can perform the respective procedural steps synchronously and together with the optical measuring device, which is also positioned so as to rotate.